15 common math questions from the SATs that everyone gets wrong

No matter how hard you study... some questions will still stump you. Joe Raedle/Getty Images

The SAT doesn't just test how good you are at math, reading, and writing — it tests how good you are at taking the SAT.

Preparing for the math section of the test requires lots of practice and memorization of some formulas, but it's also important to know how to recognize trick questions, sift through unnecessary details, and remember simple tricks like reading the entire question through before starting to work on it.

Here are 15 math problems from the SAT that people usually get wrong — with step-by-step explanations for how to solve them.

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Many people misread this question about the original price of a laptop.

You want the absolute value of x - 3 to be between six and seven, so multiple values of x work: -3.1, -3.2, etc. But the answer you would write is the absolute value of those numbers: 3.1, 3.2, etc, since that's what they're asking for.

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SAT prep site PrepScholar ranked this question as one of the hardest SAT math problems of 2016.

Quadratic functions sneak up on many people who take the SAT.

For starters, you can tell from the graph that the y-intercept is 2, which automatically eliminates "C" where the y-intercept is -2.

The vertex of the graph is at x = 0, meaning that the "b" in the quadratic equation ax 2 + bx + c has to be 0. Otherwise, the graph would be shifted to the left or right. Therefore, you can also rule out "B" and "D" using the FOIL method. (PrepScholar offers a more detailed explanation of what the FOIL method is and how to apply it to this question.)

The answer is "A," y = x 2 + 2.

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Some people forget to memorize formulas that aren't provided.

As PrepScholar explains, it's impossible to answer this question if you don't know the formulas for the sine and cosine of an angle.

"If you were a formula whiz and knew the complementary angle relationship for sine and cosine, which is sin(x°)=cos(90°−x°), you'd know immediately that the answer is cos(90°−x°)= 4/5 or 0.8," PrepScholar explains.

You can still solve this problem by drawing a diagram of the triangle, but speed is key on the math portion of the SAT, where you should allot yourself one minute per question.

Problems with percentages can also be tricky.

Let's say b = 100 and k = 25. If there are 100 bricks and 25 of them have been stacked, that means 75 bricks have not yet been stacked, or 75% of the bricks.

Which of the multiple choice answers gives you 75% when you plug in those numbers?

A: 100/7500 = 0.0133%

B: 7500/100 = 75%

C: 10,000/25 = 400%

D: 2500/100 = 25%

The answer is "B."

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If the problem involves a circle, the key is likely understanding the radius.

If there are circles involved, understanding the radius might be key.via PrepScholar

If you know the length of one radius of a circle, you know them all.

Here, the problem tells you that sides AB and AO of a triangle are equal. AO is a radius of the circle, and so is BO. The radii of a circle are always equal, so AO and BO are also the same length. That means that triangle ABO is an equilateral triangle, and all of its angles measure 60 degrees.

The answer is "D," 60 degrees.

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Don't let drawings fool you — this is a question about circles, not squiggles.